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Craig H. Bishop and Daniel Hodyss

-h DA window running from 0900 to 1500 UTC and for a 12-h DA window running from 0600 to 1800 UTC. Figure 1 gives the vertical variation of global horizontal averages of the root-mean-square (rms) error of this first guess in wind and temperature at 1200 UTC. The rms wind errors exceed 4 m s −1 at the jet level and in the stratosphere while rms temperature errors exceed 1 K throughout much of the depth of the atmosphere. Note that this “error” is entirely due to the NAVDAS assimilation of

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Monika Krysta, Eric Blayo, Emmanuel Cosme, and Jacques Verron

Zhang et al. (2009) in that the scheme is more consistent owing to the use of the SEEK smoother instead of the ensemble Kalman filter. Another important difference lies in the application context. Our interest here focuses on the midlatitude mesoscale ocean where turbulent dynamics develops through barotropic and baroclinic instabilities. The dynamical situation chosen mimics the nonlinear behavior of a midlatitude oceanic jet associated with a fully turbulent mesoscale eddy field. Altimetry being

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Thomas M. Hamill and Jeffrey S. Whitaker

: A kinetic energy backscatter algorithm for use in ensemble prediction systems. Quart. J. Roy. Meteor. Soc. , 131 , 3079 – 3102 . Snyder , C. , and T. M. Hamill , 2003 : Leading Lyapunov vectors of a turbulent baroclinic jet in a quasigeostrophic model. J. Atmos. Sci. , 60 , 683 – 688 . Szunyogh

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José A. Aravéquia, Istvan Szunyogh, Elana J. Fertig, Eugenia Kalnay, David Kuhl, and Eric J. Kostelich

. , Y. Sato , and T. Kadowaki , 2010 : Ensemble Kalman filter and 4D-Var intercomparison with the Japanese operational global analysis and prediction system . Mon. Wea. Rev. , 138 , 2846 – 2866 . Olsen , E. T. , 2007 : AIRS/AMSU/HSB version 5 data disclaimer . Goddard Space Flight Center, NASA, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 21 pp. [Available online at http://disc.gsfc.nasa.gov/AIRS/documentation/v5_docs/AIRS_V5_Release_User_Docs/V5_Data

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Mark Buehner, P. L. Houtekamer, Cecilien Charette, Herschel L. Mitchell, and Bin He

winds). Consequently the wind increment will have the effect of displacing toward the west the jet of strong northwesterly winds in the background state. For the third experiment ( Fig. 6 ), the time of the temperature observation coincides with the end of the assimilation time window. In all four results, the location of the maximum temperature increment is now upstream, that is to the northwest, of the observation location. The wind increment again forms a cell of cyclonic circulation

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Loïk Berre and Gérald Desroziers

and omega balance equations allows for the representation of some effects of the jet dynamics on space and time variations of temperature covariances in particular. Another way to relax the covariance homogeneity assumption is to represent geographical variations of variances while using the homogeneity assumption for correlations. This has been done in the European Centre for Medium-Range Weather Forecasts (ECMWF) variational assimilation system, as described in Derber and Bouttier (1999) , by

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